1. Field
One or more embodiments of the present invention relate to an organic light-emitting device, for example, an organic light-emitting device having an electron transport layer including an n-dopant.
2. Description of the Related Art
Organic light-emitting devices are self-light emitting devices that emit light when a voltage is applied thereto, and offer high luminance, high contrast, multi-color reproduction, large viewing angle, quick response rate, and low driving voltage.
An organic light-emitting device has a structure including an organic emission layer between an anode and a cathode. Upon application of a voltage, holes from the anode and electrons from the cathodes are injected into the organic emission layer. The injected holes and electrons undergo electron exchanges in adjacent molecules in the organic emission layer, thereby migrating to opposite electrodes. Upon recombination of electrons and holes in the organic emission layer, molecular excitons in a high-energy excited state are generated. The molecular excitons emit light of inherent color upon returning to a low-energy ground state.
Active-matrix organic light emitting devices (AMOLEDs) may include thin film transistors (TFTs) using amorphous silicon or polycrystalline silicon. Polycrystalline silicon is advantageous in view of its high charge mobility and being available for both n-type TFTs and p-type TFTs, but is unsuitable for large-screen displays. Meanwhile, amorphous silicon TFTs are appropriate for manufacture of large-screen displays, so there have been efforts to improve the characteristics of OLEDs using such amorphous silicon TFTs. However, amorphous silicon may have only n-channel TFTs thereon. In this case, common OLEDS with lower anodes are allowed to be only at a source terminal of a driving TFT, which affects the stability of a source voltage that is dependent on a voltage drop of organic light-emitting materials.
To address these drawbacks, an inverted OLED with a reflective metal-based lower cathode and an indium tin oxide (ITO) anode on an organic layer has been suggested. However, the organic layer underlying the ITO cathode may be damaged during deposition of ITO thereon by sputtering. For this reason, an inverted OLED with an ITO-based lower cathode has been suggested, wherein a drain terminal of a n-channel TFT is connected directly to the cathode of the OLED, so that stability may be improved with a reduced driving voltage. However, this inverted structure using a high work function ITO as a cathode requires more efficient electron injection from ITO to the organic layer.